The only way I've found so far is to use ffmpeg, which would be workable if windows-only environment, but a mac compatible version of the command-line executable is harder to come by... - there's got to be a better way, no?

The Any File plugin uses the Windows and Mac thumbnail services to get thumbnails for any file type they understand, including video (Windows Explorer on Windows, the Quick Look functionality on Mac). On Mac OS, the command-line tool "qlimage" will retrieve thumbails for any file type. On Windows, I had to write a small program that accesses the thumbnails of Windows Explorer. More than a little painful.

But in your case, perhaps you could use "ffmpeg" on Windows and "qlmanage" on Mac.